Replacing BIOS ROM on an MSX (HX-10)

By ocitygate

Expert (72)

ocitygate's picture

24-03-2021, 18:28

I have patched a BIOS. Basically I rewritten the TAPE IO routines to run at 12X speed.
At the moment I'm loading the patched BIOS into RAM. But the cassettes keep reverting to BIOS in slot 0.
Would replacing the ROM chip on my machine be a dangerous thing to do?
The BIOS is socketed (I think).

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By CASDuino

Champion (330)

CASDuino's picture

24-03-2021, 19:18

Have you tried your patched ROM in an emulator?

By ocitygate

Expert (72)

ocitygate's picture

24-03-2021, 20:22

actually i know the rom runs, i test it on a real machine but loaded into ram

By Grauw

Ascended (10713)

Grauw's picture

24-03-2021, 20:28

ocitygate wrote:

Would replacing the ROM chip on my machine be a dangerous thing to do?

If you use the correct pin compatible EPROM chip, then no.

By zoltari

Supporter (12)

zoltari's picture

28-03-2021, 00:10

If you mean the physical process of pulling and the ROM chip then yes, that is easy enough to do and it’s perfectly safe. I’ve done it myself once on a socked ROM - I just used a chip pulled and very slowly lifted the chip with the help of a thin plastic blade. I had myself earthed just in case electrostatic discharge might damage something, but honestly I don’t even think this was necessary. It seemed better to be safe and I had a proper static bracket and Earth connection available anyway, so in my case it wasn’t any hassle to do this, but touching a large metal object like a radiator or a cold tap with copper piping would be fine - as long as you’re not wearing a nylon shell-suit and shuffling about in polystyrene floor tiles or a nylon carpet as you pull the ROM I imagine you’d be fine.

I was doing a direct ROM for ROM swap, so I’ve no ideas what might be suitable as replacement chip. As far as actually pulling and replacing a chip goes though, it’s very easy and highly unlikely to cause a problem.

80s electronics are tough as hell in my experience: it’s the modern, super tiny, ultra high track / component density chips they make now that are a ultra sensitive. That’s why I have anti static gear: when you’re surface mounting components the size of a grain of rice, a tiny static spark is like a lightening bolt to them. Funnily enough the 70s ICs are sensitive as all hell to static too, maybe because they were “new technology” at that time, but by the 80s these things were rugged, well made and well proven. I love 80s electronics from that perspective - I’ve got stuff from the 80s that will still probably be working in 3021, and stuff made in 2010 that is already dead (looking at you Gizmondo and you, HP AMD laptop!).